Abstract
Penicillium rubens strain 212 (PO212) acts as an inducer of systemic resistance in tomato plants. The effect of crude extracellular extracts of PO212 on the soil-borne pathogen Fusarium oxysporum f. sp. lycopersici has been evaluated. Evidence of the involvement of soluble, thermo-labile, and proteinase-inactivated macromolecules present in PO212 crude extracts in the control of Fusarium vascular disease in tomato plants was found. Proteomic techniques and the availability of the access to the PO212 genome database have allowed the identification of glycosyl hydrolases, oxidases, and peptidases in these extracellular extracts. Furthermore, a bioassay-guided fractionation of PO212 crude extracellular extracts using an integrated membrane/solid phase extraction process was set up. This method enabled the separation of a PO212 crude extracellular extract of seven days of growth into four fractions of different molecular sizes and polarities: high molecular mass protein fraction >5 kDa, middle molecular mass protein fraction 5–1 kDa, low molecular mass metabolite fraction, and nutrients from culture medium (mainly glucose and minerals). The high and middle molecular mass protein fractions retained disease control activity in a way similar to that of the control extracts. Proteomic techniques have allowed the identification of nine putatively secreted proteins in the high molecular mass protein fraction matching those identified in the total crude extracts. Therefore, these enzymes are considered to be potentially responsible of the crude extracellular extract-induced resistance in tomato plants against F. oxysporum f. sp. lycopersici. Further studies are required to establish which of the identified proteins participate in the PO212’s action mode as a biocontrol agent.
Highlights
Soil-borne pathogenic fungi such as Fusarium oxysporum Schlechtend.:Fr. cause various plant diseases that are responsible for severe economic and agricultural losses in the world as they affect horticultural crops such as peppers, tomatoes, and cucumbers [1,2]
Control Activity of PO212 Conidia and Crude Extracts from Submerged Cultures Against FOL1A in Various types of assays were conducted in growth chambers in order to verify the involvement of extracellular and thermo-labile compounds secreted by PO212 in the culture media in their activity against FOL in tomato plants
Viability of PO212 conidia was higher than 95% in all assays prior its application in seedbeds, but viability of SCC7 and SCC14 was less than 70%
Summary
Soil-borne pathogenic fungi such as Fusarium oxysporum Schlechtend.:Fr. cause various plant diseases that are responsible for severe economic and agricultural losses in the world as they affect horticultural crops such as peppers, tomatoes, and cucumbers [1,2]. J. Fungi 2020, 6, 131; doi:10.3390/jof6030131 www.mdpi.com/journal/jof. The indiscriminate use of chemical pesticides affects the agriculture sustainability due to environment pollution, and to public health problems and the possible development of resistance by phytopathogenic fungi [4].
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